18.4. PHYSICAL STORAGE
Consider the processing of a query. After the query is verified for syntax and checked against the data dictionary for authorization, the DBMS translates the query statements to determine what data is requested. From the data entries about the tables, rows, and columns desired, the DBMS maps the requests to the physical storage where the data access take place. The query gets filtered down to physical storage and this is where the input operations begin. The efficiency of the data retrieval is closely tied to where the data is stored in physical storage and how it is stored there.
What are the various physical data structures in the storage area? What is the storage medium and what are its characteristics? Do the features of the medium support any efficient storage or retrieval techniques? We will explore answers to questions such as these. From the answers you will derive methods for improving performance. First, let us understand the types of data structures in the data warehouse.
18.4.1. Storage Area Data Structures
Take an overall look at all the data related to the data warehouse. First, you have the data in the staging area. Though you may look for efficiency in storage and loading, arrangement of the data in the staging area does not contribute to the performance of the data warehouse from the point of view of the users. Looking further, the other sets of data relate to the data content of the warehouse. These are the data and index tables in the ...
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